Question

如何使用return fetched string

编写post方法

func post(link:String,passedPostString:String) {
    let request = NSMutableURLRequest(url: NSURL(string: link)! as URL)
    request.httpMethod = "POST"


    request.httpBody = passedPostString.data(using: String.Encoding.utf8)

    let task = URLSession.shared.dataTask(with: request as URLRequest) {
        data, response, error in

        if error != nil {
            print("error=\(String(describing: error))")
            print("******Error*****")
            return

        }
        let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)

      print(responseString!)




    }
    task.resume()
}

然后我称之为

var link  = "link"
var passedPostString = "passedPostString"
print(post(link: link , passedPostString: passedPostString ))

将返回获取的值

Answer 1

dataTask方法是异步的，因此无法返回立即返回值，因为您不知道何时会调用它。

最好的办法是传入一个完成处理程序，该处理程序将从主代码中异步调用：

func post(link:String, passedPostString:String, completionHandler: @escaping (NSString) -> ()) {
    let request = NSMutableURLRequest(url: NSURL(string: link)! as URL)
    request.httpMethod = "POST"


    request.httpBody = passedPostString.data(using: String.Encoding.utf8)

    let task = URLSession.shared.dataTask(with: request as URLRequest) {
        data, response, error in

        if error != nil {
            print("error=\(String(describing: error))")
            print("******Error*****")
            return

        }
        let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)

        completionHandler (responseString!);
    }
    task.resume()
}


var link  = "link"
var passedPostString = "passedPostString"
let completion = { (result: NSString) in print(result) }
post(link: link, passedPostString: passedPostString, completionHandler: completion)

Answer 2

进行异步网络调用的函数不能具有返回类型，因为在完成之前可能需要一段时间。你不希望系统冻结并等到响应，这将超过目的。

您可以添加一个带有完成闭包的新参数，当请求完成时将调用该完成闭包：

func post(link:String,passedPostString:String, completion: @escaping (String?, Error?) -> Void) {
    let request = NSMutableURLRequest(url: NSURL(string: link)! as URL)
    request.httpMethod = "POST"

    request.httpBody = passedPostString.data(using: String.Encoding.utf8)

    let task = URLSession.shared.dataTask(with: request as URLRequest) {
        data, response, error in

        // Make sure there is no error, else..
        guard error == nil else {
            completion(nil, error)
            return
        }
        let responseString = String(data: data!, encoding: String.Encoding.utf8)

        completion(responseString, nil)

    }
    task.resume()
}

带有返回字符串的iOS swift post方法

2 个答案: